Spread half of the sliced berries on a parchment lined baking sheet in a single layer. Place in the oven to roast for 25 minutes. Remove from the oven and set aside to cool.
While the strawberries are roasting, add the remaining sliced strawberries, lemon juice, 2 tablespoons of the sugar, and cornstarch to a small sauce pan.
Let mixture come to a rolling boil over medium high heat, stirring occasionally. Once boiling, turn to low heat and let it slowly bubble for 10 more minutes.
Combine the flour, baking powder, salt, 2 tablespoons of the sugar, and lemon zest in a large bowl. In a separate small bowl whisk together the egg yolks, melted butter, vanilla, and milk.